Increasingly stringent evaporative fuel standards for automobiles and trucks demand that the fuel system component minimize the emission of fuel vapors through automotive components such as the fuel tank, fuel filler lines, fuel injector seals, and fuel seals. Fluoroelastomers such as copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), and terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) have been used for reducing fuel permeation from the above-noted fuel seal applications. However, fluoroelastomers employed in fuel seal applications generally require low temperature properties to maintain sealing performance for cold weather.
Various types of fluoroelastomers for fuel seals have been proposed to address these concerns. In general, the most successful of the elastomers generally contain perfluoromethylvinylether (PMVE). PMVE effectively reduces the glass transition temperature of the resulting polymer. However, perfluoroalkylvinylether monomers are expensive and as such the resulting fluoroelastomers are relatively high priced.